The World Trade Organization opened a formal investigation Sept. 25 into allegations China is providing a safe haven for product piracy and counterfeiting, the most far-reaching of four trade disputes between Washington and Beijing, trade officials said.

The U.S. complaint over China’s enforcement of intellectual property rights is the culmination of years of agitation in Washington and elsewhere over one of the world’s biggest sources of illegally copied goods ranging from DVDs, CDs and designer clothes to sporting goods and medications.